Leonardo da Vinci’s multi-barrel weapon concept is commonly called the 33-barrel organ.
The design consisted of three rows of eleven small cannon barrels mounted on a wheeled frame. The arrangement resembled the pipes of a musical organ, which explains its popular name. One row could be fired while another was being loaded, allowing the weapon to maintain a more regular sequence of volleys than a single cannon.
Leonardo’s design was intended to increase the rate of fire and cover a broad area. It was not a machine gun in the modern sense: the barrels were separate, black-powder artillery pieces, and the weapon did not use automatic loading or continuous fire.
The concept belongs to Leonardo’s military engineering studies, especially those made while seeking patronage from powerful Italian rulers. Surviving drawings show the general arrangement, but there is no evidence that Leonardo built and successfully deployed the complete weapon.